i wonder if you have managed to follow up on your thomas?
smith as you know can be difficult to pinpoint in any census without certain details, like the death cert, marriage cert of birth cert.
what i can tell you at the moment, unless you already know, from the igi's
andrew smith born around 1754 dundee
elizabeth duncan born around 1758 dundee
they married in mains 19th sept 1778
children from the marriage that is noted on igi's, there may well be more as there seems to be a gap in births
andrew...born 21/7/1780
barbara...born 16/12/1781
alexander...born 4/4/1784
david...christened...17/9/1786
isobel...christened...29/8/1790
george...christened...15/1/1794
thomas...christened 11/10/1795
janet...christened 8/1/1798
i am hoping someone can identify with this family and provide you with a lead
trying to help
Joe